The effect of ethyl alcohol on the antiarrhythmic action of atenolol in the adrenaline-induced arrhythmia model was studied in rats non-dependent and dependent on ethanol. Atenolol administered jointly with ethanol, in a single dose or repeatedly produced a weaker antiarrhythmic effect than when it was given alone. Moreover, a rise in animal mortality was observed, in particular after atenolol administration in the period of intoxication. No significant effect of atenolol on ethanol blood concentration was found.